Defensive publication



DEFENSIVE PUBLICATION UNITED STATES PATENT OFFICE Published at the request of the applicant or owner in accordance with the Notice of Dec. 16, 1969, 869 O.G. 687. The abstracts of Defensive Publication applications are identified by distinctly numbered series and are arranged chronologically. The heading of each abstract indicates the number of pages of specification, including claims and sheets of drawings contained in the application as originally filed. The files of these applications are available to the public for inspection and reproduction may be purchased for 30 cents a sheet.

Defensive Publication applications have not been examined as to the merits of alleged invention. The Patent Ofiice makes no assertion as to the novelty of the disclosed subject matter.

PUBLISHED JULY 28, 1970 T876,001 HEAT-RESISTANT POLYESTERS Alan Bell and David W. Abee, both P.0. Box 511, Kingsport, Tenn. 37662 Filed July 29, 1969, Ser. No. 845,874 Int. Cl. B29c 25/00,- C08g 17/00 Us. Cl. 260-75 N 0 Drawing. 8 Pages Specification A heat-resistant polyester film and method of making same is disclosed having the ability to withstand temperatures in the order of 250 C. The polyester film is made from a dicarboxylic acid comprising 80-100 mol percent terephthalic acid and 20-0 mol percent isophthalic acid, and 1,4-cycl0hexanedimethanol having at least 60 percent trans isomer content. The film made from this polyester is first biaxially stretched such that the orientation is substantially balanced in the draft and tenter directions. The film is next heat treated at a temperature of at least 245 C. while restraining it from shrinkage. The film is then subjected to a second heat treating step while allowing it to relax, thereby allowing shrinkage. 

